1. Field of the Invention
This invention relates to an apparatus for analyzing a sample by the utilization of near field light, which is radiated out of a micro-aperture probe. This invention also relates to an apparatus for evaluating the performance of a micro-aperture probe, which is used in a near field optical microscope, or the like.
2. Description of the Prior Art
As apparatuses capable of analyzing the shape or structure of a sample smaller than wavelengths of light, near field optical microscopes, such as photon scanning tunnel microscopes, have heretofore been used. The near field optical microscopes are constituted such that, for example, near field light radiated out of a micro-aperture probe may be scattered by a sample, and the intensity of the scattered light may be detected. Also, the micro-aperture probe is scanned, and a time series detection signal representing the intensity of the scattered light is taken as a function of the position of the micro-aperture probe. In this manner, information, which represents the shape or structure of the sample, is obtained.
Ordinarily, in order for the micro-aperture probe to be formed, a radiating end portion of an optical fiber is pointed with an etching process, and a metal film is then deposited on the pointed radiating end portion with a vacuum evaporation process. Thereafter, a portion of the metal film at the pointed end is removed, and an aperture is thereby formed at the pointed end.
With the near field optical microscopes having the constitution described above, the micro-aperture probe must be scanned, and the signal, which represents the position of the probe during the scanning, must be obtained. Therefore, the aforesaid near field optical microscopes has a drawback in that the structures cannot be kept simple.
The primary object of the present invention is to provide a sample analyzing apparatus, with which a shape or a structure of a sample shorter than wavelengths of light is capable of being analyzed and which has a simple constitution.
Another object of the present invention is to provide a micro-aperture probe evaluating apparatus, with which the performance of a micro-aperture probe (specifically, a distribution pattern of intensity of near field light radiated out of the micro-aperture probe), an optimum state of polarization of incident light, and the like, are capable of being evaluated accurately and easily.
The present invention provides a sample analyzing apparatus, comprising:
i) a probe of the same type as that used in a near field optical microscope, i.e. a micro-aperture probe, which is provided with a light passage aperture having a diameter shorter than wavelengths of light, the light passage aperture being formed at a radiating end of the micro-aperture probe,
ii) a light source, which produces light for sample analysis,
iii) an incidence optical system, which causes the light for sample analysis to enter into the micro-aperture probe from an entry end of the micro-aperture probe,
iv) a sample supporting member, which supports a sample at a position that is exposed to near field light radiated out of the radiating end of the micro-aperture probe,
v) an image sensing means, which receives light scattered by the sample and detects an intensity distribution pattern of the scattered light, and
vi) a displaying means, which displays the detected intensity distribution pattern.
The present invention also provides a sample analyzing apparatus, comprising:
i) a micro-aperture probe, which is provided with a light passage aperture having a diameter shorter than wavelengths of light, the light passage aperture being formed at a radiating end of the micro-aperture probe,
ii) a light source, which produces light for sample analysis,
iii) an incidence optical system, which causes the light for sample analysis to enter into the micro-aperture probe from an entry end of the micro-aperture probe,
iv) a sample supporting member, which supports a sample at a position that is exposed to near field light radiated out of the radiating end of the micro-aperture probe,
v) an image sensing means, which receives fluorescence produced by the sample exposed to the near field light and detects an intensity distribution pattern of the fluorescence, and
vi) a displaying means, which displays the detected intensity distribution pattern.
The intensity of the scattered light or the fluorescence described above is markedly low. Therefore, in the sample analyzing apparatuses in accordance with the present invention, an image sensing means having a high sensitivity, e.g. a cooled CCD image sensor, should preferably be employed.
The present invention further provides a micro-aperture probe evaluating apparatus for evaluating the performance of a micro-aperture probe, which is provided with a light passage aperture having a diameter shorter than wavelengths of light, the light passage aperture being formed at a radiating end of the micro-aperture probe, the apparatus comprising:
i) a light source, which produces light for evaluation,
ii) an incidence optical system, which causes the light for evaluation to enter into the micro-aperture probe from an entry end of the micro-aperture probe (i.e., from an end on the side opposite to the radiating end at which the light passage aperture is formed),
iii) an image sensing means, which receives traveling light radiated out of the radiating end of the micro-aperture probe and detects an intensity distribution pattern of the traveling light in a plane that intersects with a direction of travel of the traveling light, and
iv) a displaying means, which displays the detected intensity distribution pattern.
The micro-aperture probe evaluating apparatus in accordance with the present invention should preferably be provided with a collimating optical system, which collimates the traveling light radiated out of the radiating end of the micro-aperture probe and causes the collimated traveling light to impinge upon the image sensing means.
Also, the collimating optical system should preferably be combined with an image forming optical system for separating a portion of the collimated traveling light, converging the separated portion of the collimated traveling light, and thereby forming an image of the traveling light radiated out of the radiating end of the micro-aperture probe.
Further, the micro-aperture probe evaluating apparatus in accordance with the present invention should preferably be provided with a polarization control means for controlling a state of polarization of the light for evaluation, which enters into the micro-aperture probe. Alternatively, the micro-aperture probe evaluating apparatus in accordance with the present invention may be provided with means for detecting a state of polarization of the traveling light, which has been radiated out of the radiating end of the micro-aperture probe.
The intensity of the traveling light radiated out of the radiating end of the micro-aperture probe is markedly low. Therefore, in the micro-aperture probe evaluating apparatus in accordance with the present invention, an image sensing means having a high sensitivity, e.g. a cooled CCD image sensor, should preferably be employed.
The sample analyzing apparatuses in accordance with the present invention have the effects described below. Specifically, the scattered light or the fluorescence described above has an inherent intensity distribution pattern in accordance with the structure of the sample smaller than wavelengths of light. Therefore, in cases where the intensity distribution pattern with respect to each sample structure is investigated previously, the sample structure can be predicted in accordance with the displayed intensity distribution pattern of the scattered light or the fluorescence.
The micro-aperture probe evaluating apparatus in accordance with the present invention has the effects described below.
Specifically, it has been known that there is a correlation in intensity distribution pattern between the traveling light and the near field light, which are radiated out of the radiating end of the micro-aperture probe. The correlation can be found with an electromagnetic analysis utilizing a Bethe""s calculation formula, or the like. Also, the intensity distribution pattern of the near field light can be viewed directly with a near field optical microscope. Therefore, the correlation between the viewed pattern and the intensity distribution pattern of the traveling light can be found previously.
With the micro-aperture probe evaluating apparatus in accordance with the present invention, the intensity distribution pattern of the traveling light, which has been radiated out of the radiating end of the micro-aperture probe, can be detected by the image sensing means and displayed on the displaying means. The intensity distribution pattern of the near field light can then be found in accordance with the displayed pattern and the aforesaid correlation, which has been found previously, and the performance of the probe can thereby be evaluated.
As described above, in the micro-aperture probe evaluating apparatus in accordance with the present invention, the traveling light, which has been radiated out of the radiating end of the micro-aperture probe may be collimated by the collimating optical system, and the collimated traveling light may be caused to impinge upon the image sensing means. In such cases, the intensity distribution pattern of the traveling light can be viewed directly.
Also, the collimating optical system may be combined with the image forming optical system for separating a portion of the collimated traveling light, converging the separated portion of the collimated traveling light, and thereby forming an image of the traveling light radiated out of the radiating end of the micro-aperture probe. In such cases, adjustment of a focusing point can be carried out by viewing the image, which is formed by the image forming optical system. Therefore, the traveling light can be collimated accurately.
Further, the micro-aperture probe evaluating apparatus in accordance with the present invention may be provided with the polarization control means for controlling a state of polarization of the light for evaluation, which enters into the micro-aperture probe, or the means for detecting the state of polarization of the traveling light, which has been radiated out of the radiating end of the micro-aperture probe. In such cases, it becomes possible to find the state of polarization of the traveling light, which yields an optimum intensity distribution pattern of the traveling light (and, consequently, an optimum intensity distribution pattern of the near field light).